In order to improve the preservability of content of plastic packing containers, it has heretofore been an accepted practice to form the container wall in a multi-layer structure using a polyester resin as the inner and outer layers, and using, as an intermediate layer, a functional resin such as an ethylene/vinyl alcohol copolymer or a xylylene group-containing polyamide resin for improving gas-barrier property or a cyclic olefin copolymer for improving water vapor (water)-barrier property.
In order to further improve the function such as gas-barrier property or to further impart any other function, it is also a practice to blend a functional resin with an inorganic filler or any other resin composition. For example, JP-A-2004-142944 discloses blending a xylylene group-containing polyamide with a surface modified clay in order to further improve the gas-barrier property of the xylylene group-containing polyamide resin.